The present invention relates to an opening device provided at a hole in a packaging sheet material. In particular, the invention relates to a synthetic plastics material opening device which has been directly injected moulded on the sheet.
Opening devices of different types provided on a packaging container formed by packaging sheet material and adapted for containing substances such as foodstuffs, and in particular for containing liquid beverages such as juices, water, milk, wine, etc. are known.
Examples of such opening device include a hole on a wall part of the packaging container and a plastics material lid device attached to the wall part and covering the hole in a closed state. The lid device includes a circumferential base attached to the wall part, for example by means of adhesives, circumferentially surrounding the hole, and a lid element hinged to the base. The hole may be a perforation, and once the lid element is opened, the perforation may be engaged and forced open so that the contents inside the packaging container may be dispensed therefrom. Alternatively the hole may be a circumferential hole punched in the sheet. A sealing element such as an aluminium pull tab is connected to the wall part so as to cover the opening, and once the lid element has been opened, the sealing element may be removed to expose the opening for dispensing the contents of the packaging container.
Opening devices which include a perforated hole on the sheet present the disadvantage that when the perforation is broken by the user, material portions from the perforation may become dislodged from the sheet and mix with the contents inside the container. In the case of opening devices which include a hole punched in the sheet, the provision of the sealing element connected to the sheet for closing the hole adds additional requirements for apparatus and method steps for forming the opening device on the sheet, thereby reducing the overall efficiency of the formation of the opening device on the sheet. Both these types of opening devices also have the disadvantage that a separate lid device must be attached to the sheet, in which the lid device is formed in a separate method and apparatus thereby adding costs related to a separate manufacturing line and to separate storage and transport of the lid devices so as to even further reduce the efficiency of the opening device formation on the lid.
Moreover, both these types of opening devices are subject to the problem of edge soaking, in which the edge of the perforation or hole in the sheet comes into contact with the contents of the package thereby to compromise the stability of the sheet and package. Generally, the packaging sheet material is formed of several layers including an inner paper layer and two outer synthetic plastics material coating layers, one of which is destined to form a product contact surface. Other possible layers such as printing ink layers, laminating layers and aluminium foil layers may be interposed between the paper layer and the outer coating layers. The hole or perforation in the sheet will expose the internal layers of the sheet at such hole or perforation, and unless such edge is adequately sealed the packaged product may come into contact with the internal layers of the packaging sheet material possibly causing damage to the product and/or the package. In the case of the opening devices provided with a circumferential hole, extra steps have been taken to provide a patch for sealing the hole edge, which however even further reduces the efficiency in the opening device manufacture.
A further problem encountered in the above-described opening devices, due to the fact that the base is positioned circumferentially distant from the hole or perforation, is that after a certain amount of product is poured out of the container, residual product often remains inside the lid device, in contact with the outer surface of the sheet between the hole or perforation and the base of the lid device. Precise placement of the base on the sheet so that it is flush with the hole is unfeasible, and the consequence of residual product left in contact with the outer surface of the container is fastidious to the user. Moreover, in these known opening devices, while the lid device may be reclosable, once the perforation or hole has been opened, the package is not resealable in the sense that the hole or perforation is not itself reclosed or resealed.
As an alternative to the above opening devices, in which an already formed plastics material lid device is applied to the sheet, U.S. Pat. No. 4,725,213 discloses a plastics material opening device which is injection moulded directly onto the sheet of packaging material. In particular, a pair of mould tools are moved into arrangement about a prestamped hole in the sheet, and heated thermoplastics material is injected through an injection passage defined between one of the mould tools and one surface of the sheet and extending along such surface of the sheet in order to form the opening device at the prestamped hole. The mould tools are shaped so that the formed opening device includes a pair of circumferential flange portions each of which is attached to the opposite surfaces of the sheet at the edge of the prestamped hole, thereby attaching the opening device to the sheet.
The mould tools consist of a pair of mould tools which are both movable in opening and closing directions which extend perpendicularly to the extension of the sheet. Such a moulding configuration in U.S. Pat. No. 4,725,213 substantially limits the flexibility of the device in forming opening devices which different shapes, since the mould tools in their release movement must not encounter any portions of the opening device which protrude in a direction perpendicular to the direction of movement of the mould tools.
The opening device in U.S. Pat. No. 4,725,213 moreover includes a lid which is torn off at weakened lines without any provision for reclosing or resealing of the package after the lid is removed.
Another problem encountered with conventional opening devices attached to packaging material sheets is that the opened lid portion frequently is positioned to hinder the dispensing operation of the contents of the package.
Another problem which exists with opening devices attached to sheet holes consists in that the provision of the hole in the sheet frequently weakens the mechanical strength of the sheet. Packages made of these sheets with opening devices attached at the sheet holes are generally stored and shipped in stacks, and the weakening of the sheet at the holes may lead to collapse and damage of the container during shipping and storing. A possible solution for compensating for the sheet hole weakness would be to provide opening devices having parts extending for large areas about the sheet hole. However, such provisions would lead to increased manufacturing costs due to increase in material requirements and production difficulties and inefficiency in forming and attaching the larger parts to the sheet. In the case of direct injection moulding of the opening device, for example, increased times would be required for injecting into larger mould cavities, leading to a significant decrease of efficiency of the production line.
It is seen that there exists a need in the field of packaging sheet material opening devices to provide opening devices having an improved functionality. Moreover, it is desirous that opening devices provided at holes in sheets are of such a nature so as to be manufacturable in the most effective and efficient manner possible.
In accordance with one preferred aspect of the invention, there is provided an opening device attached at a hole in a top wall portion of a packaging container and positioned adjacent a fold line of the packaging container, in which a base portion of the opening device includes a main circumferential portion circumferentially enclosing the extension of the hole and a protruding portion which protrudes from the main circumferential portion towards the fold line. The extension of the protruding portion towards the fold line of the container allows to strengthen the packaging material sheet by distributing forces to the fold line, such that containers provided with the opening device may be stacked for storage and transport without collapse. Moreover, the protruding portion constitutes a small portion of the base portion with respect to the main circumferential portion, so as to maintain efficiency of manufacture of the opening device by requiring minimised material amounts and simplified procedures.
The opening device according to another preferred aspect of the invention includes a tamper evidence protrusion which extends from a lid portion of the opening device to be connected to an outer side of the sheet. A user is therefore assured that the container has not been tampered with when the tamper evidence protrusion is stably connected to the outer side of the sheet. Such tamper evidence protrusion further functions as a pull tab for opening the lid portion.
In accordance with still another aspect of the invention, a reduced thickness tearing edge is provided between the base portion and the lid portion. In a preferred embodiment, first and second end portions of the tearing edge are thinner still that two connecting lateral portions of the tearing edge, so that the initial and final tearing actions of the lid are extremely easy thereby to reduce undesirable abrupt movements to the container at the initial and final tearing actions and to make the entire removal procedure of the lid portion essentially smooth and uniform.
The opening device according to a further aspect of the invention, there are provided lower and upper ring portions respectively of a lid portion and a base portion of the opening device which are mutually connected by a tearing edge. Once the lid portion has been removed from its connection with the base portion, the upper and lower ring portions may be mutually intermated in a releasably locked manner, so as to reseal the opening device. In a most preferred embodiment, one of the ring portions is releasably lodged inside the other ring portion in a snap-type arrangement.
The opening device according to another preferred aspect of the invention includes a bistable hinge connecting the lid portion to the base portion, such that in the open position of the lid portion with respect to the base portion, the bistable hinge releasably biases the lid portion to stably remain in its open position.
The technical characteristics and advantages of the present invention will become apparent to those skilled in the art from the following detailed description of some preferred embodiments thereof, described and illustrated in the accompanying drawings only by way of non-limitative example, wherein like reference numerals indicate like parts.